Stereoscopic display systems are supposed to deliver a discrete left-eye image and a discreet right-eye image to the respective viewer's eyes. However many single-screen displays such as video monitors or projection screens, when used for stereoscopic display, exhibit crosstalk, wherein each eye not only receives the image intended for it, but also the image intended for the other eye at a reduced intensity. This results in ‘ghosts,’ where each eye sees objects on the display, with a faint copy of the object nearby.
Ghost-compensation systems can compute a pair of compensated images that are projected for viewing by each eye. The compensated image for the left eye is equal to the image intended for the left eye minus an intensity-scaled version of the image intended for the right eye, and vice versa. The amount of the intensity scaling is approximately equal to the amount of the crosstalk.
Thus, in a system having a crosstalk c, left eye image L and right eye image R, the compensated image for the left eye L′ would equal L-cR and the compensated image for the right eye R′ would equal R-cL.
When the compensated images L′ are projected for viewing by the respective eye in the presence of the crosstalk, what is perceived by the left eye would be L′+cR′ or (L−cR)+c(R−cL), which is about (1−c2) L. In other words, this is an image having no ghosting from the right eye image. Likewise, when the compensated images R′ are projected for viewing by the respective eye in the presence of the crosstalk, what is perceived by the right eye would be R′+cL′ or (R−cL)+c(L−cR), which is about (1−c2) R.
Systems such as those described by Cowan et. al in U.S. Patent Application Publication No. 20060268104 entitled “Ghost-Compensation for Improved Stereoscopic Projection,” the compensated images can be pre-computed and stored for later playback, or can be computed on the fly in real-time during playback of non-compensated images.
The drawback of pre-computing the compensated images is that different stereoscopic display systems can exhibit different crosstalk values, in which case the pre-computed compensated images suitable for one stereoscopic display are not well suited for another. This produces an inventory control problem, where the operator of a display system must acquire the version of a presentation prepared for the correct crosstalk value.
While a real-time ghost-compensation system can be configured to match the crosstalk of stereoscopic display, for systems involving one or more of high resolution, high frame rate, non-linear encoding, or encryption, the cost and complexity of the decryptions, transforms, frame buffers, array math, inverse transforms, re-encryption, etc. is substantial. The latency of such a system can affect the lip-sync of a presentation. The security requirements associated with content can require additional decryption and encryption keys, which must be inventoried, tracked, and managed.
Thus, there is a significant need for a ghost-compensation system that is real-time but does not require any additional transforms or encryption steps. There is also a need for this system to compensate for a wide range of crosstalk values.